I called their Home Max number again (0844 873 8586, option 2 then option 1) at 6:22 and ascertained that their office hours start at 07:00. I will call them at about 07:05 to see what happens, I am interested in what they have to say about the situation.

Time of checking: 06:30
Attainable download rate (kbps): 480
Downstream Rate (kbps): 416
Upstream Rate (kbps): 160
Home phone line: Offline
VOIP line: Online